The Edge of the World
by queer-space-mermaid
Summary: "Cheerless, hard, imprinted with the ghost of every horror he had witnessed, his eyes would never linger too long on Cas these days." Destiel past relationship. Castiel POV. End!Verse. Mermaid!AU


**A/N:** Written for the GGE17. For Amber.

 **Warnings:** Depressing, drug use.

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Though a man of so few summers, he carried a weight so crushing that it stooped his shoulders like those of an old man. He hunched like the overturned, decrepit hull of a shipwreck. Once twinkling with passion, his green eyes had faded like seaweed abandoned on the shore. Cheerless, hard, imprinted with the ghost of every horror he had witnessed, his eyes would never linger too long on Cas these days.

Indeed, Cas could not recall the last time Dean had said his name. The Commander of the Resistance barked orders, argued over strategy, ripped into soldiers who had slipped up. It was not in him anymore to be gentle, vulnerable, hushed. Everything he said was tainted with a harsh bitterness that left no space for the delicate, no place for the sacred. Cas liked to think that was why Dean never spoke his name now.

Cas held little practical significance to the Commander at this point. A used sponge, every last drop of useful intelligence had been squeezed out. Siren tactics, Lucifer-related lore, a map of the sea surrounding the archipelago and the current leading to the Darkest Depths. Bare of tail, he was undisguisable from the hordes of seaman-cum-soldiers converged on the island camp.

They were assembled in the briefing tent this morning. Dean loomed over the map that spread over the desk in the middle. He pointed towards an X near the east islands.

"Scouts have found wave disturbances here. The siren we captured last week also mentioned this location, so we can be pretty sure this is Lucifer's current base. We don't have much time to attack before he disappears again, so we need to move fast."

The other soldiers nodded, serious and determined.

"When should we be ready to leave, Commander?" Lieutenant Chuck asked.

Dean chewed his tongue, regarding the map for a few beats. Cas watched the close-shaven Adam's apple dart in his neck. Dean met the Lieutenant's eyes grimly. "Tomorrow, dawn."

Dean began assigning roles to the men. Cas was to join a party directly attacking Lucifer's guard. _Suicide mission_ , he thought but did not say.

Back in his own tent, Cas laid supine. The sunlight streamed in through the fabric above, blotted out in parts by the shadows of leaves, shaking in the breeze. A pale imitation of the glittering ocean. His nails dug into the soft flesh of his legs, fingertips damp.

The hushed crash of waves against the shore whispered in a language that was now slippery in his mind. He understood only enough to justify the deep and foreboding anxiety brewing in his guts. _Darkness_ , the sea hissed. _Danger... Death..._ He both ached to hear the lost words scattered by the wind, and wished he could block out those few he could still decipher.

Cas rolled onto his stomach and scrabbled for the pouch of herb he had bought from one of the well-travelled seaman. Though his hands trembled, muscle memory let him roll the joints swiftly. He inhaled deeply, holding the breath in his lungs as he counted back from ten. As the air whooshed out again, he closed his eyes and watched the water whip around him.

 **…**

The _Impala_ towered over Castiel, water frothing around the hull. He swum back far enough to see the people on the trawler's deck. Three men adjusted a massive net, the leftmost old and weathered, the one on the right exceptionally long and lanky, and the one in the middle almost blocked out by the bright sun behind. He slowly came into focus. Lean and muscular frame, short brown hair, high cheek bones. His lips full, his chin stubbly, and his eyes radiant. He glowed golden.

 _And then…_

Moonlight illuminated the trawler, as calamitous waves tossed it to and fro. A strong current pulled Castiel back, and his tail spasmed painfully as he kicked to remain in place. Lightning punctuated the blackened sky, rain streaked the air. And the golden man clung to the bow like a starfish to a rock. His mouth opened in a yell, but his voice was drowned out by thunder, as he struggled to maintain his grip. Just as he began to hoist himself back over the side of the boat, a pale arm rose from the water and snatched his ankle. Screeching and clawing, the sickly white siren dragged the golden man down in a straight dive.

 _And then…_

Castiel kicked furiously to the surface, the golden man heavy and limp in his arms. The storm was raging so fiercely that he hardly realised when they broke the surface. He undulated like a dolphin across the water, with the man's arms draped around his neck and his head hanging over Castiel's shoulder. His stillness burnt cold into Castiel's chest, as they raced towards the island. With a final burst of energy, he hauled the man onto the jetty.

The rain was tapering off now, but the wind still whistled harshly in Castiel's ears. He hoisted himself up and turned the man onto his side. A rush of salty water poured out of his mouth.

"Please," Castiel whispered, trying to shield him from the elements. He held the golden man's face, aglow in the flickering light of a lantern fastened to a nearby post. He watched anxiously for a sign of life. But the man had gone blue and did not stir.

Castiel took a shaky and unfamiliar breath through his mouth, then leant down. A breath of life. Another and another.

The man spluttered, rolled to his side, and coughed his guts up. He sucked in lungfuls of air, hands spread wide over the splintery wood of the jetty. Finally, he started to recover.

Castiel was met with his wide green eyes.

"Who are you?" the man gasped. His gaze trailed across to Castiel's vivid silver tail. "Wh-what are you?"

 _I am Castiel_.

The man winced and his hands shot up to cover his ears.

 _I am a mermaid of-_

The man hissed. The nearby lantern shattered.

Castiel cleared his throat, fumbling to use his mouth and tongue as articulators.

"I am Castiel, mermaid of Poseidon," he rasped. Lightening flashed overhead, lighting his face starkly. "I am the one who gripped you tight and raised you from perdition."

 **…**

In the biting cold witching hour, the flaps of Cas's tent burst open. There was no moonlight to illuminate the figure crouching in the opening, but Cas's eyes were attuned to the dark. He stared at Dean, heartbeat thudding in his ear. Dean stared back, unmoving and silent.

Longing threaded through his ribs and curled his fingers, aching in his chest and watering in his eyes. The air dry and restless blew through the tent, paying no mind to the current of yearning emanating from Cas. In but two steps, Dean could be in his arms. In but two steps, he could resume his rightful place, resting on Cas's chest, head nestled into the crook of Cas's neck. Warm and safe and home.

Such fantasy was torment. For not two steps, nor two thousand could bridge the ocean of distance between the men now. Dean's capacity for love had drowned with his brother's soul. Standing before Cas was a cruel and capricious ghost. As warm and as comforting as a shadow.

He disappeared, leaving the entrance of Cas's abode flapping in the wind. The only comfort Cas nursed in this heart was the conviction that this night would be his last.

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 **A/N:** All reviews would be appreciated. :)


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